Glow discharge tube



Jan. 31, 1956 T. JURRIAANSE ET AL 2,733,372

GLOW DISCHARGE TUBE Filed July 10, 1951 INVENTORS TOM JURRIAANSE.

JAN HORSELI NG AGEN United States Patent Ofiice 2,733,372 Patented Jan. 31, 1956 GLOW DISCHARGE TUBE Tom Jurriaanse, The Hague, and Jan Horseling, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application July 10, 1951, Serial No. 235,972 Claims priority, application Netherlands July 19, 195i] Claims. (Cl. 313-485) The invention relates to glow discharge indicator tubes, in which the length of the glow discharge is a measure of the current strength.

These tubes are used, for example, in apparatus for measuring low gas pressures, comprising a glow discharge tube with a magnetic field.

In tubes of this kind it is generally desired that with low current strength the discharge should take place from a particular point of the cathode and that the length of the glow discharge should be a linear function of the current strength.

Anodes and cathodes for this purpose have previously been constituted by two wires arranged in a position flush with one another, the anode having a sharp bend toward the cathode. This construction indeed fulfills the requirement that in the case of low current strength the glow discharge should concentrate on a particular point i. e. opposite the sharp bend in the anode wire, but the straight line relationship between the length of the glow discharge and the current strength is not too satisfactory, and the glow discharge readily shifts in the case of high current strength.

According to the invention these disadvantages are avoided by constructing the anode and the cathode in the form of two parallel wires and by arranging, at the end of the cathode, an auxiliary anode, also constituted by a wire, preferably in line with the cathode. When the tube operates, the auxiliary anode takes a low current, which, however, is sufiicient to cause the glow discharge produced by the discharge current to the main anode to apply invariably at the same area Thus a fixed starting point is obtained and the linearity is excellent, even in the case of low current strength. Moreover, the ignition of the main discharge is facilitated. The best results are obtained, when the cathode is made of a metal having a melting point of more than 1400 C., the wall of the discharge tube being coated with a visible but substantially light transparent layer of similar material, preferably molybdenum. In this case the tube has constant properties for many thousands of hours. I

A particularly preferred embodiment 18 obtained by constructing the tube in a symmetrical form with two long electrode wires arranged parallel to one another, and auxiliary anodes in line with said electrode wires on sides remote from each other. The two long electrode wires may, in this case, operate as the cathode or as the anode.

The invention willnow be described in detail with reference to the accompanying drawing, in which the sole figure shows a glow discharge tube according to the invention.

Referring to the drawing, 1 designates the glass wall of the glow discharge tube, 2 and 3 designate two parallel wires of molybdenum, the cathode and the anode of the tube. a

Opposite the free end of each of the Wires auxiliary electrodes 4 and 5 respectively of molybenum are provided having annular appended extensions 6 and 7 respectively. The latter serve to coat the tube wall with volatilised molybdenum even at the extremity of the tube. A suitable gas filling of neon at a few millimeters of mercury pressure is provided.

What we claim is:

l. A glow discharge indicator tube in which the length of the glow discharge is an indication of the current strength, comprising an elongated tubular transparent envelope containing an ionizable low-pressure gaseous medium at a pressure at which a discharge is sustained in said medium, a pair of straight elongated wire-like electrodes disposed in said envelope parallel to one another and extending longitudinally throughout most of the length of the envelope, one of said electrodes being an anode and the other a cathode, said cathode and anode electrodes each being supported only from a difiereut end of said envelope to prevent interference with the glow discharge therebetween, and an unactivated wire-shaped auxiliary anode disposed inside said envelope adjacent the unsupported end of said cathode electrode.

2. A glow discharge indicator tube in which the length of the glow discharge is an indication of the current strength, comprising an elongated tubular transparent envelope containing an ionizable low pressure gaseous medium at a pressure tained in said medium, a pair of straight elongated wirelike electrodes disposed in said envelope parallel to one another and extending longitudinally throughout most of the length of the envelope, one of said electrodes being an anode and the other a cathode, said cathode and anode electrodes each being supported only from a different end of said envelope to prevent interference with the glow discharge therebetween, and a pair of unactivate dwire-shaped auxiliary anodes disposed inside said envelope each adjacent the unsupported end of one of said electrodes.

3. A glow discharge indicator tube in which the length of the glow discharge is an indication of the current strength, comprising an elongated tubular transparent envelope containing an ionizable low pressure gaseous medium at a pressure at which a discharge is sustained in said medium, a pair of straight elongated wire-like refractory metal electrodes disposed in said envelope parallel extending longitudinally throughout most of the length of the envelope, one of said electrodes being an anode and the other a cathode, said cathode and anode electrodes each being supported from a difl erent end of said envelope to prevent interference with the glow discharge therebetween, an unactivated wire-shaped auxiliary anode having an annular extension disposed inside said envelope adjacent the unsupported end of said cathode electrode, and a substantially light transparent refractory metal wall coating on the inner wall of said envelope.

4. A glow discharge indicator tube in which the length of the glow discharge is an indication of the current strength, comprising an elongated tubular transparent envelope containing neon at a pressure of a few millimeters of mercury, a pair of straight elongated wire-like electrodes disposed in said envelope parallel to one another and extending longitudinally throughout most of the length of the envelope, one of said electrodes being an anode and the other a cathode, said cathode consisting of a metal having a melting point of more than 1400 C., said cathode and anode electrodes each being supported only from a different end of said envelope to prevent interference with the glow discharge therebetween, an unactivated wire-shaped auxiliary anode disposed inside said envelope adjacent and in line with the unsupported end of said cathode electrode, and a substantially light transparent coating of visible thickness on the inner at which a discharge is sus-.

wall of the envelope and consisting of the same metal as that of the cathode. ,3

5. A glow discharge indicator tube in which the length of the glow discharge is an indication of the current strength, comprising an elongated tubular transparent envelope containing neon at a pressure at a few miiiimeters of mercury, a pair of straight elongated wire-like molybdenum electrodes disposed insaid envelope parallel to one another and extending longitudinally'throughout most of the length of the envelope, one of said electrodes being an anode and the other a cathode, said cathode and anode electrodes each being supported only from la-difierent end of said envelope to prevent interference with the glow discharge therebetween, an unactivated wire-shaped auxiliary molybdenum anode having an annular extension disposed inside said envelope adjacent the unsupported end of said cathode electrode, and a substantially light transparent molybdenum coating on the inner wall of said envelope.

References Cited inthe file of this patent UNITED STATES PATENTS 

